In general, a projector is a device for projecting a strong beam of light on an image embodied in a panel, namely, an LCD panel and projecting an image signal on an external large-sized screen through a projection lens. Hereinafter, an LCD projector utilizing the LCD panel as a panel will be described.
FIG. 1. is a perspective view showing a state that an upper casing of a conventional LCD projector has been removed, FIG. 2 illustrates a perspective view of a synthesizing system area of the conventional LCD projector, and FIG. 3 illustrates an exploded perspective view of FIG. 2. As shown in the drawings, the LCD projector includes a casing 11, a projection lens 13 for projecting a beam synthesized by a synthesizing system 31 onto an external screen (not shown), an illuminating system 21 having a beam source (not shown) provided at an inner side of the casing 11 and a plurality of optical lenses, optical filters and reflection mirrors, which are not shown in the drawings, for dividing a beam irradiated from the beam source into three color beams, that is, a red color beam, a green color beam, and a blue color beam, and forming three optical paths.
A synthesizing system 31 is disposed between the illuminating system 21 and the projection lens 13 for synthesizing divided beams and providing the beams to the projection lens 13, and a cooling system 61 and cooling system casing 63 is provided for cooling the synthesizing system 31.
An illuminating system casing 22, which divides beams irradiated from the beam source mounted therein into three color beams of red, green and blue, and forms three paths for each beam, is disposed at a peripheral area of the synthesizing system 31.
Moreover, the synthesizing system 31 includes a plurality of dichroic prisms 35 mounted in predetermined intervals and parallel to each other, on a plurality of LCD panels 33, and a prism holder 37 for supporting the dichroic prisms 35.
The prism holder 37 includes a holder body 39 having a horizontal part 41 arranged parallel to a bottom surface of the casing 11 and a vertical member 45 vertically placed on the side of the horizontal part 41. The vertical member 45 has a center passage through which the projection lens 13 is inserted, and top and bottom plates 49 and 51 respectively are placed at the top and bottom of each prism 35 to provide support for the prisms 35.
Furthermore, the prisms 35 are provided on three sides other than the side in which the projection lens 13 is connected. Adjacent prisms 35 are arranged at a right angle to each other, and an upper plate 49 is connected to an upper part of the prisms 35 for fastening the prisms 35 in relative positions to one another. Additionally, the top plate 49 has a plurality of screw holes 50 for fastening a fixed board 34 supporting the LCD panels 33 with fixing screws 42.
The vertical member 45 of the holder body 39 has a plurality of screw holes 47 at both sides thereof for connecting the illuminating system casing 22. The screw holes 47 are separated from each other along a vertical direction. The horizontal part 41 has a seating portion (not shown) for seating the bottom plate 51, to which the prisms 35 are connected. The seating portion has LCD panel connecting holes 43 in a circumferential area thereof for arranging the LCD panels 33, parallel to each other, on an outer side of each prism 35.
Meanwhile, if light projected from the beam source is divided by the illuminating system 21 and passes the corresponding LCD panels 33, each LCD panel 33 is increased in temperature due to an increase of heat flux. Furthermore, generally, if the temperature of the LCD panel 33 is increased by more than a prescribed temperature, namely, critical temperature, elements are damaged. Therefore, a cooling means (not shown) is provided for cooling the synthesizing system 31 through inducing the outside air in an adjacent area (especially, an upper portion) of the synthesizing system 31, or for discharging the inside air to the outside.
However, components of a conventional LCD projector as described may be moved from an original position due to vibration of the cooling fan, causing deterioration in image quality. For example, the optical path of the prisms 35 and/or the LCD panels relative to the optical paths of the projection lens 13 may be disturbed, and pixel positions of three color beams projected to the LCD panels and formed on the screen are different from each other.
Meanwhile, in the case of an LCD projector which is installed on the ceiling, a fixed board 34 supporting the LCD panel 33 at the upper portion may become misaligned due to the effects of repeated vibration, as well as gravity, causing misalignment between the LCD panels 33 and/or the prisms 35 to the respective optical paths.